2nd Incident - AD Login Not Working!

I need detailed instructions on how to resolve this; this is the 2nd incident of same issue. First issue was resolved via remote phone support, with the conclusion that the ServiceDesk server is loosing communication with the domain controller for unknown reasons.

Currently, we are not able to log into ServiceDesk with active directory username/password combos. We are also not able to log in using our username/username/local. We are also not able to log in with administrator/administrator/local, so I have no way to get into the program to do any further troubleshooting or adjusting.

I have added the DC to the hosts file as a previous post suggested; that did not help.

Please advise on how this can be resolved as quickly as possible. We are totally down.